Definition
Malignant melanoma is a highly malignant tumor that quickly forms metastases in other organs. As the name suggests, it originates from the melanocytes of the skin. Almost 50% of all melanomas develop from pigmented moles. However, they can also develop “spontaneously” on completely inconspicuous skin.
Occurrence in the population (epidemiology)
Melanoma is the tumor with the highest increase in incidence worldwide. In Germany, the so-called incidence increases by 8% every year. Incidence rates (melanoma 100.
000 people/year) are lowest in sub-Saharan Africa with 0.1. In Australia, the incidence rate is the highest at 60. In Germany, the incidence is about 12100,000 per capita per year.
Due to improved early detection, mortality has been reduced to 20% of all cases. Melanomas are usually detected between the ages of 30 and 70. There are various risk factors for the development of melanoma.
A malignant melanoma can develop from a mole (nevus cell nevus) that has existed for years. It can also develop from completely inconspicuous skin. For example, genetic factors play a role.
An increased risk of melanoma development is seen in FANN repair damage (see below), or in a family history of melanoma. Acquired factors, such as severe sunburns, can also promote the development. It is estimated that the following distribution of causes exists:
- 30 to 70% of melanomas develop from long existing moles
- 30 to 70% of melanomas develop on inconspicuous skin
- 10 to 20% of melanomas develop after years from melanotic precancerosis = precancerous stages (e.g. lentigo maligna). In this case, precancerosis is a change in the skin that may degenerate into a tumor.
- 10% of melanomas are familial melanomas:Within the family group of familial melanomas there are several nevi (moles) that can be considered:
- Clark nevus
- Familial atypical nevus and melanoma (FAMM) syndrome
Stage setting of a melanoma
Malignant melanoma is divided into 5 stages according to the so-called TNM classification. This classification is based on the following three criteria: In addition to these three main criteria, there are two secondary criteria that serve to subdivide the 5 stages: According to these criteria, stage 0 corresponds to a tumor that grows only locally and has a low mitosis rate without metastasizing. In stage I the tumor thickness is <2mm and there are no lymph nodes affected nor are there distant metastases.
Stage II differs from stage I in that the tumor is now >2mm. From stage III onwards, the lymph nodes are also affected, but there are no distant metastases. Only from stage IV onwards are distant metastases present.
The lower the stage, the better the prognosis.
- The mitosis rates. This criterion describes the number of cell divisions of the tumor and thus its activity.
This measurement is particularly relevant for prognosis in tumors with a thickness of less than 1 mm.
- The ulcerations. This refers to the tumor’s ability to cause deep skin damage that resembles a wound or ulcer. The more pronounced this process is, the more advanced the tumor is.
- The tumor thickness (T).
It is important to determine how deep the tumor has penetrated the skin. Below one millimeter, the risk of metastasis is very low, whereas above 4 mm there is a very high probability of metastasis of the malignant skin tumor. The reason for this is that the tumor connects to the blood and lymph vessels that are located in the deeper skin layers and over which the tumor can spread.
- The infestation of regional lymph nodes (N).
These are the lymph nodes closest to the tumor. Due to their location in relation to the tumor, they are the first to be affected by metastasis and are therefore a good indicator of the stage of malignant melanoma. A distinction is made between metastases that are only visible under the microscope and metastases that have already led to a palpable or visible enlargement of the lymph nodes.
- The remote metastases (M).
These are the spread of the tumor to other parts of the body. In malignant melanoma there are no preferred organs that are affected by metastases, as is typical for other tumors. Occurrence in the liver, lungs, brain, bones and skin is possible.The special feature of malignant melanoma is metastasis in the heart. Since a malignant disease of the heart is very rare, this metastasis accounts for about 50% of all cardiac tumors.
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